Conventional bicycle chains are manufactured as a succession of inner links alternating with outer links. Each outer link consists of a pair of opposite and spaced plates, hinged at their ends, at the respective inner faces, to a pair of plates that constitute the inner links. The inner links define a gap smaller than that defined by the outer links, but still sufficient to house a tooth of a sprocket or of a crown of the respective bicycle. The plates that constitute the inner links are kept spaced apart through pins that, during operation, go into abutment on the sides of the teeth of the sprockets or of the crowns of the bicycle.
The plates that form the inner and outer links of the transmission chain are provided with through holes. In the final assembling step of the chain, an articulating pin is inserted in the aligned holes of an outer link and of an inner link. In this way, the inner links are hinged to the outer ones. In other words, the aligned holes of an outer link and of the corresponding inner link provide for the seat of an articulating pin.
The articulating pin is not just a hinge between the links of the chain, it also has the task of transferring, during pedaling, the mechanical stresses from the inner links to the outer ones, and vice-versa, without undergoing deformations. In other words, the articulating pin is the linking element between the links of the chain intended to transfer the mechanical loads, mainly the traction forces. Within this meaning, the articulating pin distinguishes itself from the simple locking or reinforcing elements often provided in conventional chains.
Usually, the solutions available on the market provide assembling of the chain through riveting of the articulating pin. The pin comprises a head having a greater diameter than the diameter of the holes of the links. Once the pin has been completely inserted in the links, the head of the pin goes into abutment against the outer face of a first plate of the outer link, at a first hole. The portion of the pin opposite to the head, i.e. the distal portion, is riveted, i.e. is subjected to a permanent plastic deformation by means of which a counter-head is obtained. The diameter of the counter-head is greater than the diameter of the second hole present on the second plate of the outer link. In this way, the articulating pin is locked at its ends against the disengagement from the links. The riveting is often carried out manually by means of a suitable tool, equipped with a punch capable to be at least partially inserted in the distal portion of the pin and with thrusting means of the punch.
The insertion of the articulating pins in the corresponding links to assembly a chain is a delicate step, since imprecise insertion may cause the local deformation of the chain and may jeopardize its functionality. Normally, chains are sold in an open condition and the end user has the task of inserting the last articulating pin to configure the chain at the desired length. Also in the circumstance in which a used chain must be disassembled and assembled again it is necessary to insert an articulating pin to articulate the final links.
Normally, the links of a chain that are subject to the extraction of the relative pin are replaced with new links. The new links are available in repair kits that also include the articulating pins. Also for new links it is necessary to provide for the maximum precision of insertion of the corresponding articulating pin. Disadvantageously, repair kits are relatively expensive.